1. Field of the Invention
The present invention relates to a cathode for electrolysis of water or of an aqueous solution of an alkali metal chloride such as sodium chloride, and having sufficiently low hydrogen overvoltage characteristics. The present invention relates also to a process for producing the cathode.
2. Description of the Related Art
The industry of water electrolysis or aqueous alkali metal chloride electrolysis consumes a large amount of electric power. Various techniques therefore are being developed for energy-saving. The energy saving can be achieved by substantial reduction of the electrolysis voltage which depends on theoretical electrolysis voltage, solution resistance, diaphragm resistance, anode overvoltage, cathode overvoltage, and so forth. The overvoltage, which is affected greatly by the electrode material and the electrode surface state, attracts attention of many scientists, and many techniques have been developed therefore. In the ion-exchange process for sodium chloride electrolysis, concerns are concentrated to the reduction of the anode overvoltage, and comprehensive researches and developments have been made. Consequently, anodes have been completed which have sufficient durability and involve few problems of overvoltage are almost solved. The anodes are employed widely at the moment.
On the other hand, many studies have been made also for reduction of the cathode overvoltage. For the iron cathode having hydrogen overvoltage of 400 mV, electrodes are disclosed which reduces the overvoltage by 200-250 mV from the overvoltage of the iron electrode. For example, JP-A-59-25940 and JP-A-6-146046 disclose electrodes having a hydrogen absorbing alloy or a platinum group oxide deposited on the surface of an electrode base material. JP-B-40-9130 discloses an electrode having an alloy of a transition metal such as iron, cobalt, and nickel with tungsten or molybdenum electroplated on the surface of the electrode base material.
However, the aforementioned electrode having a hydrogen absorbing alloy or a platinum group oxide deposited thereon is costly owing to expensiveness of the material, whereas the electrode coated with an alloy of the latter patent is not satisfactory in reducing the hydrogen overvoltage.
After comprehensive investigations to solve the above problem, the present invention has been accomplished.